The field of the invention is intracardiac procedures. More specifically the present disclosure provides methods for improved intracardiac surgery and intracardiac delivery of therapies and devices.
Intracardiac procedures are most easily performed on a heart that is not beating or that has minimal blood flow therethrough. Cardiopulmonary bypass and chemical arrest using cardioplegia solutions have traditionally provided surgeons with suitable operative conditions: hemodynamic control and cardiac quiescence. This technique has contributed to technical success in increasingly complex cardiac surgical operations. However, it would be advantageous to have methods for conducting intracardiac procedures with the heart in a blood-filled but non-beating state.
Surgeons have also used cardioplegia, fibrillators, or clamps to stop blood flow in their working field. Adenosine has been shown to be safe and effective in creating transient cardiac standstill and has been used during balloon coronary and valvular dilatation procedures and implantation of stents and grafts. Another method of producing a heart without blood flowing therethrough is rapid ventricular pacing.
Rapid ventricular pacing causes the heart to beat at approximately 200 to 400 beats/min, which functionally means that the heart is in continuous contraction, never fills with blood between beats, and therefore the flow of blood through the heart is stopped. Rapid ventricular pacing produces a heart that is in contractile, rigid “arrest” and has the disadvantage of not providing a generous intracardiac space in which to work. Rapid ventricular pacing is functionally “systolic arrest”. It stresses the myocardium to contract so rigorously and repeatedly and this may induce myocardial injury, especially when prolonged rapid pacing is performed in patients with hypertrophic or ischemic myocardium.
Another method that creates brief periods of heart stillness is taught in U.S. Pat. No. 6,479,523 and related patents. This patent teaches methods for creating controlled intermittent asystole (CIA) and using CIA during brief intervals required for placing anastomotic sutures. This method is taught to be especially useful for use in placing anastomotic sutures during minimally invasive direct coronary artery bypass (MIDCAB) surgery, for example. CIA is suitable for improving the precision of coronary anastomoses performed on a beating heart and reducing graft failure while increasing ease of operation. This patent does not discuss in detail the use of CIA for minimally invasive intracardiac access or procedures.
It has now been discovered that controlled intermittent asystole can be employed by minimally invasive means to specifically enable novel catheter-based intracardiac technologies and therapies by placing the heart in a relaxed state, in which its chambers are intentionally distended by passive inflow of blood and thereby expanded to create generous working space within the cardiac chambers. This creates an intracardiac environment in which the surgeon has better access to intracardiac anatomic structures and adequate space in which to maneuver instruments, catheters, and imaging devices. The motionless, relaxed, capacious state of the heart during CIA is in sharp contrast to the variable state of the heart during normal beating or its hypercontracted state during rapid ventricular pacing.
This particular method of “controlled intermittent asystole” is termed “controlled intermittent diastolic arrest” (CIDA) herein. The heart is placed in an intentional state of inactivity with the chambers expanded and filled with blood for the purposes of performing intracardiac procedures such as valvular repair or replacement, ventricular remodeling procedures, implantation of intracardiac devices, therapeutics, gene therapy, stem cell therapy, angiogenic therapy etc., rather than epicardiac procedures, such as coronary artery bypass grafting.